U.S. patent application Ser. No. 197,695 filed Oct. 16, 1980, now abandoned, discloses a fuel control system for dramatically increasing the fuel efficiency of motor vehicles. That system includes a meter valve for supplying gas to the carburetor under ordinary operating conditions and also includes a by-pass valve for supplying gas under unusual conditions such as during acceleration of the vehicle. The present invention relates to a method and arrangement for incorporating both of such valves in a common mounting block which may be conveniently adapted to the system.